1. Field of the Invention
The present invention relates to field of retractable wheel systems for launching and recovery of boats in water, and for transportation of boats overland. The wheels may be adjusted to positions suitable for land transportation and for water travel, and are coupled by a transverse member such that the wheels are deployed or stowed as a single unit.
2. Description of the Prior Art
The prior art includes a number of examples of boat-attached wheel systems which are manufactured for long distance transportation, but which are unsuitable for intermittent convenience transport of the boat because of their complicated mechanical structure and their concomitant cost. Examples include Kury (U.S. Pat. No. 4,515,102), Buckner (U.S. Pat. No. 3,185,330), Sundin (U.S. Pat. No. 3,113,686), H:son Gullberg et al. (U.S. Pat. No. 3,779,573), Helbig (U.S. Pat. No. 3,733,628) and Wasserlein (U.S. Pat. No. 2,622,893).
Boat attached wheel systems are also known which require that the boat be inverted to be wheeled about, because the wheels protrude upwardly. This type of device is unsuitable for moving a loaded boat, and for launching and recovering the boat, because a boat cannot be loaded or floated until positioned upright. Such systems include Wolfe (U.S. Pat. No. 3,499,177).
Boat attached wheel systems are further known which teach separate and independently-operated left and right wheel assemblies. Where the wheels are deployed or stowed one at a time, the boat and its operator are "off balance" when only one of the wheels is deployed. This "off balance" position can be dangerous in small boats which are easily capsized. Examples of these systems include Brockelsby (U.S. Pat. No. 3,986,723), Zoretic (U.S. Pat. No. 3,284,821), Totten (U.S. Pat. No. 2,929,079), Wolfe (U.S. Pat. No. 3,499,177), Kury (U.S. Pat. No. 4,515,102) and Johnson (U.S. Pat. No. 3,982,292).
Retractable wheel systems for launching boats as known in the prior art typically are such that the wet wheels are moved into the people-occupied area of the boat when stowed, where they take up scarce space and may get the contents and/or occupants of the boat wet. In the alternative, some retractable wheel systems in the prior art bring the wheels up along the lateral sides of the boat, thus occupying the limited side access and/or viewing space along the sides. It would be more appropriate if possible to reserve the side space for passenger use as needed for fishing, rowing or the like. Examples of retractable wheel systems with these shortcomings include Brockelsby (U.S. Pat. No. 3,986,723), Kury (U.S. Pat. No. 4,515,102), Johnson (U.S. Pat. No. 4,567,844), Norrby (U.S. Pat. Nos. 2,999,252 and 3,295,864), Jalowiecki (U.S. Pat. No. 3,154,799) and Harvey (U.S. Pat. No. 2,042,598).
The prior art typically provides a wheel axle arrangement with a single deployed or operating position along the longitudinal axis of the boat. However, when a boat is loaded and unloaded from an end, its overall center of gravity moves forward or backward along its length. While supporting the boat on its wheels the operator must bear a portion of the weight of the boat and contents which is proportional to the distance between the boat's center of gravity and the operational axle position. Hinnant (U.S. Pat. No. 4,422,665) teaches a means to move a boat wherein it is possible to vary the wheel position; however, this is because there is no fixed assembly of relocatable wheels attached to the boat. The boat is moved onto the device which is then strapped into place. The boat is launched from the device and recovered onto the device. The wheel bearing device itself does not remain with the boat while the boat is being operated, but instead is left on shore. Once strapped in place, no provision is made for relocating the wheels to accommodate changes to the center of gravity due to loading or unloading.
Detachable wheel mountings as in Hinnant are subject to the possibility that the mountings will fall off the boat during the launching and recovery phase of the operation. It is conceivable that the mountings could be lost entirely in the water. A further example is shown in Wild (U.S. Pat. No. 3,453,002).